The invention relates to the manufacture of laminated panels or doors for use in furniture such as cabinets and the like. In particular, the invention relates to the manufacture of inexpensive panel and door members which may have the appearance and weight of far more expensive materials such as hand carved hardwoods. The face and sides of the panels are formed through the action of heat and vacuum from flat relatively thin sheets of a plastic such as polystyrene so as to produce a three dimensional self-supporting shell which may include very fine detail such as wood grain. As noted in Susnjara U.S. Pat. No. 3,943,022, assigned to a common assignee, such thermoformed shells are bonded to rigid backing boards to achieve a desired stiffness or rigidity. Generally, a hot melt adhesive is applied to the inside of the shell and the backer is very carefully assembled into the recess in the back of the shell. If the resulting product is to have an appearance of the shell and backer being integral, it is important that the edges engage the backer tightly and that the adhesive be evenly distributed. Achieving proper assembly is most difficult and time consuming since the desired tight fit usually prevents one backer edge from being inserted into the shell if the opposite edge is permitted to move to the bottom of the shell recess. The loss of adhesive from the contacting edges during assembly can be prevented by squirting the adhesive between the edges with a pointed tip dispenser in a separate operation subsequent to assembly. However, such a secondary operation is time consuming, does not get the adhesive on the shell shoulder underlying the back member, and is not satisfactory in the corner areas where the tool cannot reach but where the plastic is most resistant to being fastened since it is quite stiff. Finally, the secondary hand gluing operation can result in the application of insufficient adhesive with poor bonding. On the other hand, the application of too much adhesive is not only wasteful but can permit adhesive to ooze out of the joint where it must be removed before the finished shell-backer assembly can be sanded and finished. If a very rapidly setting adhesive is used, the assembler has no extra time to get a balky backer into the shell recess so that the parts cannot be assembled correctly if the adhesive has already started to set. A slower setting adhesive allows more assembly time but also requires substantial clamping time to hold the assembled components until the adhesive has set.